Update classes and structure for attachments list.
Update classes and structure for attachments list.

gaapt/bookyt,hauledev/bookyt,silvermind/bookyt,xuewenfei/bookyt,silvermind/bookyt,huerlisi/bookyt,wtag/bookyt,huerlisi/bookyt,wtag/bookyt,xuewenfei/bookyt,hauledev/bookyt,silvermind/bookyt,hauledev/bookyt,gaapt/bookyt,wtag/bookyt,gaapt/bookyt,huerlisi/bookyt,xuewenfei/bookyt,hauledev/bookyt,gaapt/bookyt,silvermind/bookyt